获取dom元素尺寸位置信息
function getDomRect(elem) {
var rect = elem.getBoundingClientRect();
var top = rect.top;
var bottom = rect.bottom;
var left = rect.left;
var right = rect.right;
var width = rect.width || right - left;
var height = rect.height || bottom - top;
var X = left + (document.documentElement.scrollLeft || document.body.scrollLeft);
var Y = top + (document.documentElement.scrollTop || document.body.scrollTop);
return {
bottom: bottom,
height: height,
left: left,
right: right,
top: top,
width: width,
X: X,
Y: Y
};
}